Not at all, PM3 aren’t exactly user friendly.
They are more about capability rather than ease of use.
Designed by geeks, for geeks 
Not ideal, but Whatever works.
Just the other day I suggested to somebody else to do a clean rebuild, but I think you might be better to persist, it should just be a couple of commands
There are a couple of Mac users here, but the majority are either Linux or Windows, so we either need to wait or go researching
@Zwack suggestion sounds valid and logical, but if it doesn’t work, let us know,…
infact, I just had another thought.
Where you are typing your commands, to the left of the prompt, does it say Proxmark3 OR PM3?
If it says PM3, try typing in
cd Proxmark3
or
cd -
Hopefully you end up with Proxmark3 left of prompt.
Then try those commands again
brew upgrade --fetch-HEAD proxmark3
pm3-flash-all
laughing at myself; the time it took me to write this, I should have just looked it up…
Oh well, let’s just wing it…for now